Abstracts

Rationale: Subtle alterations in both white (WM) and grey (GM) matter have been described in patients with idiopathic generalized epilepsy (IGE); while controversies about thalamic abnormalities have been extensively evaluated, fewer studies have focused attention of cortical abnormalities. Besides, the impact of pharmacoresistance on structural alterations is not entirely clear. Therefore, here, we compared WM and GM cortical abnormalities between patients free of seizures (SZ-FREE) and patients with recurrent seizures (SZ-PERSISTENT). Methods: We analyzed 68 IGE patients [38 SZ-PERSISTENT (patients with current seizures during the previous year of MRI, 25 women, median 33years); 30 SZ-FREE (free of any type of seizures for at least one year before MRI, 20 women, median 33years)], compared to 68 controls matched for age (p=0.96) and gender (p=1). High resolution T1-weighted scans acquired on 3T PHILIPS were analyzed with CAT12/SPM12/MATLAB 2014 (www.neuro.uni-jena.de/cat). Using automated routines, individual cortical maps were extracted from each hemisphere. Before group comparisons, all resulted images were resampled and then smoothed with a 15mm kernel. Diffusion Tensor Images (DTI, 32 directions) were processed with ExploreDTI/MATLAB 2014 (www.exploredti.com). Ten tracts [3 parts of the corpus callosum (CC), Corticospinal tract (CST), Inferior Fronto Occipital (IFO) tract, Inferior Longitudinal Fasciculus (ILF), dorsal and parahippocampal cingulum (PH-CINGULUM), uncinate and body of fornix (FORNIX)] were delineated by semi-automatic deterministic tractography to yield fractional anisotropy (FA). SPSS22 was used for univariate, multivariate analyses and Chi-square tests, while CAT12/SPM12 was used to compare GM surface maps between patients and controls with T-tests between patients and paired controls. SPM results are displayed with minimum T-statistic of 3.2, p Results: Both groups were balanced for syndromes (Juvenile Myoclonic epilepsy, juvenile absence and tonic-clonic generalized only, p=0.49). GM analyses with Surface Based Morphometry (SBM) revealed a more severe pattern of cortical alterations in SZ-PERSISTENT group, mainly in bilateral precentral and superior frontal gyri. Alterations in temporal lobe were more intense on SZ-FREE group (Figure 1).Multivariate analyses with Repeated-measures ANOVA for bilateral tracts (CST, cingulum, PH-cingulum, IFO, ILF and uncinate) revealed significant FA reduction mainly on SZ-PERSISTENT group (p MANOVA of Corpus Callosum segments and FORNIX also showed more alterations on SZ-PERSISTENT group (Figure 2). Conclusions: Patients with recurrent seizures presented more abnormalities in both GM and WM, while those who were free of seizures (any type of seizures) showed a less severe pattern of GM alterations. Our results reveal a negative impact of persistent seizures on brain structure in IGE, which has not been presented before. We believe  further investigation is necessary involving functional neuroimaging as well. Future studies should include correlations between structural and functional characterisics with both psychological and cognitive performances. Funding: FAPESP - BRAINN(2013/07559-3)FAPESP - Akari Ishikawa (2013/07559-3)FAPESP -Marina Polydoro (2015/10228-4)FAPESP - Danielle Garcia (2016/03307-8)